1. Technical Field of the Invention
The present invention relates to a recoil starter for an internal combustion engine, and in particular, to a recoil starter having buffering/power-accumulating means interposed between a driving member and a driven member.
2. Description of the Related Art
A conventional recoil starter which is designed to be mounted on an internal combustion engine is generally provided with a driving member having a rope reel around which a recoil rope is wound, and a driven (idler) member comprising a centrifugal ratchet mechanism. In order to start the internal combustion engine, the recoil rope (recoil handle) is pulled to revolve the rope reel. The resulting revolution of the rope reel is then transmitted, via the driven member, to the crankshaft of the internal combustion engine to thereby start the engine.
The present inventors have heretofore proposed a modification of the aforementioned recoil starter in Japanese Patent Application No. H11-238642. In the modified recoil starter, a spiral spring mechanism is interposed as buffering/power accumulating means between the driving member and the driven member. Since the spiral spring mechanism is interposed between the driving member and the driven member, a load from the engine side may be buffered while the recoil rope is pulled during the first-half of the driving process, namely, until the piston of the internal combustion engine reaches the top dead center thereof. Moreover, the pulling force of the recoil rope is simultaneously accumulated in the spiral spring mechanism. During the second-half of the driving process, the pulling force accumulated in the spiral spring mechanism during the first-half of the driving process is combined with the pulling force effected in the second-half of the driving process to thereby generate a resulting force, which is utilized for starting the internal combustion engine.
As a result, it is possible to minimize a fluctuation in the pulling force of the rope so as to smooth the rope-pulling operation, thus enabling even a person having a weak physical strength to easily start the engine.
However, this type of conventional recoil starter requires unidirectional rotating means having a one-way clutch, in order to prevent the spiral spring mechanism from reversely rotating together with the rope reel. In other words, in order to enable the spiral spring mechanism (of the spiral spring case) to rotate only in the driving direction (the direction of rewinding the spiral spring) when the recoil rope is rewound, unidirectional rotating means, with a one-way clutch, is interposed between the inner peripheral portion (the cylindrical boss portion) of the spiral spring case and a fastening shaft which is fixed to a starter case.
Since the one-way clutch is interposed between the inner peripheral portion of the spiral spring and the fastening shaft, the diameter of the one-way clutch is inevitably required to be relatively small. Hence, it is difficult to make the one-way clutch sustain a large magnitude of torque. Furthermore, the components of a recoil starter of this type are required to be mechanically strong, rigid and precise, thus making the recoil starter inevitably larger in weight and more expensive.
Accordingly, there exists a need in the art for a recoil starter which can overcome the aforementioned disadvantages associated with the conventional recoil starter with unidirectional rotating means having a one-way clutch.
An object of the present invention is to provide a recoil starter having an improved unidirectional rotating means which is capable of sustaining larger magnitudes of torque thereby making it possible to utilize parts of lower mechanical strength and precision, to lighten the weight thereof, to reduce the manufacturing cost thereof, and to simplify the working and assembling thereof.
These and other objects of the invention, which will become apparent with reference to the disclosure herein, are accomplished by the recoil starter according to the present invention, which comprises a driving member, a driven (idler) member, and buffering/power-accumulating means interposed between the driving member and the driven member. The buffering/power accumulating means includes a housing disposed in the proximity of the driving member, an actuating pulley disposed in the proximity of the driven member, a buffering/power accumulating member interposed between the housing and the actuating pulley, and unidirectional rotating means disposed on the outer peripheral side of the housing for unidirectionally rotating the housing. The buffering/power-accumulating means is adapted, during a driving process of the driving member, to buffer a load from an engine side and to accumulate a force supplied by the driving of the driving member while alleviating impact to the driven member, and the driven member is arranged to be actuated by the accumulated power.
In a preferred embodiment, the unidirectional rotating means includes a one-way clutch. The one-way clutch preferably includes one or more claw members swingably supported by one of the fixing portion of a starter case and the housing, one or more urging members for urging the one or more claw members toward the other of the starter case and the housing, and one or more engaging portions provided on the other of the starter case and the housing, wherein at least one of the claw members is adapted to be engaged with at least one of the engaging portions, thereby preventing the housing from being rotated in the direction opposite to the driving direction.
Preferably, the one-way clutch includes two claw members which are mounted on the starter case so as to be disposed around the rotational axis of the housing and equally spaced from each other at an angle of 180 degrees. The one-way clutch in the preferred embodiment also includes three engaging portions which are provided in the housing and spaced from each other at an angle of 120 degrees.
Alternatively, the one-way clutch may include two claw members mounted on the starter case so as to be disposed around the rotational axis of the housing and spaced apart at angle of 180 degrees, with four engaging portions which are provided in the housing and equally spaced apart from each other at an angle of 90 degrees.
The buffering/power-accumulating means preferably includes a spiral spring mechanism comprising a spiral spring as a buffering/power-accumulating member, and a spiral spring case functioning as the aforementioned housing.
The driving member preferably includes a rope reel having a recoil rope wound therearound, with recoiling urging means for reversely revolving the rope reel so as to rewind the recoil rope, and with a recoil ratchet mechanism for transmitting the torque of the rope reel to the housing.
The driven member preferably includes an interlocking pulley having a power transmission mechanism, through which the driven member is interlockingly coupled with the driving member.
The power transmission mechanism is preferably constituted by a centrifugal ratchet mechanism.
Preferably, the spiral spring comprises an outer circumferential wound portion where a predetermined number of turns of the outer portion of the spiral spring are closely contacted with each other under a freely released condition of the spiral spring, and an inner circumferential wound portion which is constituted by at least one turn of the inner portion of the spiral spring, wherein a clearance is provided between the outer circumferential wound portion and the inner circumferential wound portion. In a more preferred embodiment, the outer circumferential wound portion is constituted by a third turn and the following turns successive to the third turn, and the inner circumferential wound portion is constituted by a first turn and at least a portion of the second turn which is closely contacted with the first turn.
According to the preferable embodiments of recoil starter of the present invention as described above, the unidirectional rotating means e.g., a one-way clutch for unidirectionally rotating the housing, is disposed on the outer peripheral side of the housing, thus allowing the diameter of the aforementioned unidirectional rotating means to be increased. Consequently, in contrast to the conventional recoil starter where the unidirectional rotating means are interposed between the inner peripheral portion of the spiral spring and the fastening shaft, it becomes possible according to this improvement to make the one-way clutch mechanism sustain a torque of large magnitude. Additionally, it is no longer necessary that the component parts have high mechanical strength, rigidity or precision. As a result, the manufacturing cost of the recoil starter can be reduced while, at the same time, its reliability can be improved and its weight reduced.
In accordance with the invention, the objects as described above have been met, and the need in the art for a recoil starter that is light and has a compact configuration, and which has enhanced reliability, has been satisfied.